In addition to these evidence-based recommendations, the guideline development group also identifies points of best clinical practice in the original guideline document.
Levels of evidence (Ia-IV) and grading of recommendations (A-C) are defined at the end of the "Major Recommendations" field.
Does Combined Oral Contraception Increase the Risk of Venous Thromboembolism (VTE)?
B - The relative risk of venous thromboembolism is increased with combined oral contraceptive use. Nevertheless, the rarity of venous thromboembolism in women of reproductive age means that the absolute risk remains small.
Risk of Venous Thromboembolism
B - Combined oral contraceptives containing levonorgestrel or norethisterone are associated with a lower risk of venous thromboembolism than those containing desogestrel or gestodene.
B - A levonorgestrel- or norethisterone-containing combined oral contraceptive should be advised as a pill of first choice. However, after counselling, a woman may choose a desogestrel- or gestodene-containing combined pill.
B - The relative risk of venous thromboembolism increases in the first 4 months after starting combined oral contraception. This risk decreases with increasing duration of use, although it remains above that of non-users. After discontinuation, VTE risk falls to that of non-users within 3 months.
Does Progestogen-Only Contraception Increase the Risk of Venous Thromboembolism?
Progestogen-Only Contraception
B - Progestogen-only pills, injectables, and levonorgestrel implants do not increase the risk of venous thromboembolism.
Medical Eligibility for Hormonal Contraceptive Use
C - Assessing medical eligibility before prescribing allows contraception to be provided appropriately and safely without introducing unnecessary medical barriers.
The World Health Organization (WHO) Medical Eligibility Criteria for Contraceptive Use (WHOMEC) provides systematically developed, evidence-based recommendations to facilitate selection of the most appropriate method of contraception without unnecessary medical barriers. Eligibility, rather than ineligibility (or contraindication), is described. (WHO category 1: "unrestricted use"; WHO category 2: "benefits generally outweigh risks"; WHO category 3: "risks usually outweigh benefits"; WHO category 4: "unacceptable health risk"). Eligibility criteria for combined contraception (oral and transdermal) and progestogen-only, relevant to VTE, are summarised in Table 2 in the original guideline document.
Current or Previous Venous Thromboembolism
C - Women with current venous thromboembolism should not use hormonal contraception.
C - Women with a personal history of venous thromboembolism should not use combined oral contraception but may use progestogen-only methods.
Postpartum
C - A woman who is less than 21 days postpartum should not use combined oral contraception.
C - Combined oral contraception can be used after day 21 postpartum if a woman is not breastfeeding.
C - The progestogen-only pill, implant, or injection can be used safely before day 21 postpartum, even if a woman is breastfeeding.
Combined oral contraceptives affect the quality and quantity of breast milk and are not advised for breastfeeding women [Evidence level IV]
Post-Abortion
C - Combined oral contraception can be commenced immediately following first- or second-trimester abortion.
C - Progestogen-only contraception can be commenced immediately following first- or second-trimester abortion.
Smoking
B - Smokers over the age of 35 years should not use combined oral contraception but progestogen-only methods can be used.
Body Mass Index
B - Women with a body mass index over 30 should first consider progestogen-only methods, but combined oral contraception can be used after counselling.
Surgery
C - Combined oral contraception should be discontinued at least 4 weeks before major surgery where immobilisation is expected.
C - Progestogen-only methods need not be discontinued prior to surgery even when immobilisation is expected.
C - Hormonal methods do not need to be discontinued before minor surgery without immobilisation.
Other Conditions Which May Predispose to Venous Thromboembolism
Superficial Venous Thrombosis
The WHOMEC recommends that the benefits of combined oral contraception (COC) and progestogen-only contraception (POC) outweigh the risks in women with varicose veins and superficial thrombophlebitis (WHO 1 and WHO 2, respectively).
Sickle Cell Disease
WHOMEC advises that benefits of combined contraception and POC use by women with sickle cell disease outweigh the risks (WHO 2 and WHO 1, respectively).
Women with pulmonary hypertension should be advised against the use of combined contraception.
Inflammatory Bowel Disease
WHOMEC does not address inflammatory bowel disease. Faculty of Family Planning and Reproductive Health Care (FFPRHC) guidance suggests that women with inflammatory bowel disease should be offered the same contraceptive choices as other women. Women who are immobilised due to disease exacerbation require counselling regarding stopping COC.
Is Screening for Thrombophilia Needed Before Prescribing Hormonal Contraception?
C - Routine thrombophilia screening prior to hormonal contraceptive use is not recommended.
C - A thrombophilia screen may be considered in a woman with a history of venous thromboembolism in a first-degree relative under the age of 45 years who, after counselling, still wishes to use combined oral contraception.
Summary
- For most women, COC is a safe method of contraception. Although the relative risk of VTE is increased, the absolute risk remains very small.
- Progestogen-only methods (pills, injectables, implant, and intrauterine system) do not appear to be associated with increased risk of VTE. However, evidence regarding these methods is limited and absence of evidence does not equate to absence of risk.
- Heavy smoking, obesity, and underlying thrombophilia increase the risk of VTE and these factors must be taken into account when making contraceptive choices.
- Women with previous VTE should be advised against the use of COC but a progestogen-only method may be used.
- There is no place for routine screening for thrombophilia prior to contraceptive prescribing.
Definitions:
Grading of Recommendations
Grade A - Requires at least one randomised controlled trial as part of a body of literature of overall good quality and consistency addressing the specific recommendation (evidence levels Ia, Ib)
Grade B - Requires the availability of well-conducted clinical studies but no randomised clinical trials on the topic of recommendations (evidence levels IIa, IIb, III)
Grade C - Requires evidence obtained from expert committee reports or opinions and/or clinical experience of respected authorities. Indicates an absence of directly applicable clinical studies of good quality (evidence level IV)
Levels of Evidence
Ia: Evidence obtained from meta-analysis of randomised controlled trials
Ib: Evidence obtained from at least one randomised controlled trial
IIa: Evidence obtained from at least one well-designed controlled study without randomisation
IIb: Evidence obtained from at least one other type of well-designed quasi-experimental study
III: Evidence obtained from well-designed non-experimental descriptive studies, such as comparative studies, correlation studies, and case studies
IV: Evidence obtained from expert committee reports or opinions and/or clinical experience of respected authorities
